Ubuntu Manpage: direvent.conf - configuration file for direvent(8).

NAME

       direvent.conf - configuration file for direvent(8).

DESCRIPTION

       The configuration file consists of statements and comments.

       There are three classes of lexical tokens: keywords, values, and separators. Blanks, tabs,
       newlines and comments, collectively called white space are ignored except as they serve to
       separate  tokens. Some white space is required to separate otherwise adjacent keywords and
       values.

COMMENTS

       Comments may appear anywhere where white space  may  appear  in  the  configuration  file.
       There  are  two  kinds  of  comments:  single-line  and  multi-line comments.  Single-line
       comments start with # or // and continue to the end of the line:

           # This is a comment
           // This too is a comment

       Multi-line or C-style comments start with the two characters /* (slash, star) and continue
       until the first occurrence of */ (star, slash).

       Multi-line  comments  cannot  be  nested.   However,  single-line comments may well appear
       within multi-line ones.

   Pragmatic Comments
       Pragmatic comments are similar to the usual single-line comments, except that  they  cause
       some  changes  in  the way the configuration is parsed.  Pragmatic comments begin with a #
       sign and end with the next physical newline character.

       #include <FILE>
       #include FILE
              Include the contents of the file file.  Both forms are equivalent.  The  FILE  must
              be an absolute file name.

       #include_once <FILE>
       #include_once FILE
              Same  as  #include, except that, if the FILE has already been included, it will not
              be included again.

       #line num
       #line num "FILE"
              This line causes the parser to believe, for purposes of error diagnostics, that the
              line  number  of the next source line is given by num and the current input file is
              named by FILE. If the latter is absent, the remembered file name does not change.

       # num "FILE"
              This is a special form of the #line statement, understood  for  compatibility  with
              the C preprocessor.

STATEMENTS

Simple statement
A simple statement consists of a keyword and value separated by any amount of whitespace.
Simple statement is terminated with a semicolon (;).

The following is a simple statement:

pidfile /var/run/direvent.pid;

See below for a list of valid simple statements.

A value can be one of the following:

number A number is a sequence of decimal digits.

boolean
A boolean value is one of the following: yes, true, t or 1, meaning true, and no,
false, nil, 0 meaning false.

unquoted string
An unquoted string may contain letters, digits, and any of the following
characters: _, -, ., /, @, *, :.

quoted string
A quoted string is any sequence of characters enclosed in double-quotes ("). A
backslash appearing within a quoted string introduces an escape sequence, which is
replaced with a single character according to the following rules:

Sequence Expansion ASCII
\\ \ 134
\" " 042
\a audible bell 007
\b backspace 010
\f form-feed 014
\n new line 012
\r charriage return 015
\t horizontal tabulation 011
\v vertical tabulation 013

In addition, the sequence \newline is removed from the string. This allows to
split long strings over several physical lines, e.g.:

"a long string may be\
split over several lines"

If the character following a backslash is not one of those specified above, the
backslash is ignored and a warning is issued.

Two or more adjacent quoted strings are concatenated, which gives another way to
split long strings over several lines to improve readability. The following
fragment produces the same result as the example above:

"a long string may be"
" split over several lines"

Here-document
A here-document is a special construct that allows to introduce strings of text
containing embedded newlines.

The <<word construct instructs the parser to read all the following lines up to the
line containing only word, with possible trailing blanks. Any lines thus read are
concatenated together into a single string. For example:

<<EOT
A multiline
string
EOT

The body of a here-document is interpreted the same way as a double-quoted string,
unless word is preceded by a backslash (e.g. <<\EOT) or enclosed in double-quotes,
in which case the text is read as is, without interpretation of escape sequences.

If word is prefixed with - (a dash), then all leading tab characters are stripped
from input lines and the line containing word. Furthermore, - is followed by a
single space, all leading whitespace is stripped from them. This allows to indent
here-documents in a natural fashion. For example:

<<- TEXT
The leading whitespace will be
ignored when reading these lines.
TEXT

It is important that the terminating delimiter be the only token on its line. The
only exception to this rule is allowed if a here-document appears as the last
element of a statement. In this case a semicolon can be placed on the same line
with its terminating delimiter, as in:

help-text <<-EOT
A sample help text.
EOT;

list A comma-separated list of values, enclosed in parentheses. The following example
shows a statement whose value is a list of strings:

option (wait, stderr);

In any context where a list is appropriate, a single value is allowed without being
a member of a list: it is equivalent to a list with a single member. This means
that, e.g.

option wait;

is equivalent to

option (wait);

Block Statement
A block statement introduces a logical group of statements. It consists of a keyword,
followed by an optional value, called a tag, and a sequence of statements enclosed in
curly braces, as shown in the example below:

watcher {
path /etc;
event create;
}

The closing curly brace may be followed by a semicolon, although this is not required.

MACRO EXPANSION

Arguments of some statements undergo macro expansion before use. During the macro
expansion any occurrence of ${NAME} is replaced by the value of macro NAME. Macro names
follow the usual convention: they begin with a letter and contain letters digits and
underscores. The curly braces around the NAME are optional. They are required only if
the macro reference is followed by a character that is not to be interpreted as part of
its name, as in ${command}string.

The following macros are defined:

file Name of the file covered by the event.

genev_code
Generic (system-independent) event code. It is a bitwise OR of the event codes
represented as a decimal number.

genev_name
Generic event name. If several generic events are reported simultaneously, the
value of this variable is a list of event names separated by space characters.
Each name corresponds to a bit in genev_code.

self_test_pid
The PID of the external command started with the --self-test (-T) option. If
direvent is started without this option, this variable is not defined.

sysev_code
System-dependent event code. It is a bitwise OR of the event codes represented as
a decimal number.

sysev_name
System-dependent event name. If several events are reported, the value of this
variable is a list of event names separated by space characters. Each name
corresponds to a bit in sysev_code. See the section SYSTEM DEPENDENCIES in
direvent(8), for a list of system-dependent event names.

GENERAL SETTINGS

       user NAME;
              Sets the user to run as.  NAME must be a name of an existing user.

       foreground BOOL;
              Run in foreground.

       pidfile FILE;
              Upon successful startup store the PID of the daemon process in FILE.

       debug NUMBER;
              Set debug level.  Valid NUMBER values are 0 (no debug) to 3 (maximum verbosity).

LOGGING

       While connected to the terminal direvent outputs its diagnostics and debugging messages to
       the standard error.  After disconnecting from the controlling terminal it closes the first
       three  file  descriptors  and  directs  all  its  output  to  the syslog.  When running in
       foreground mode, its messages are sent both to the standard error and to the syslog.

       The following configuration statement controls the syslog output:

         syslog {
             facility STRING;
             tag STRING;
             print-priority BOOL;
         }

       The statements are:

       facility STRING;
              Set syslog facility.  STRING is  one  of  the  following:  user,  daemon,  auth  or
              authpriv,  mail,  cron,  local0  through  local7  (case-insensitive), or a facility
              number.

       tag STRING;
              Tag syslog messages with STRING.  Normally the messages are tagged with the program
              name.

       print-priority BOOL;
              Prefix each message with its priority.

       An example syslog statement:

           syslog {
               facility local0;
               print-priority yes;
           }

WATCHER

The watcher statement configures a single event watcher. A watcher can control several
events in multiple pathnames. Any number of watcher statements is allowed in the
configuration file, each one of them declaring a separate watcher.

watcher {
path PATHNAME [recursive [NUMBER]];
file STRING-LIST;
event STRING-LIST;
command STRING;
user NAME;
timeout NUMBER;
option STRING-LIST;
environ ENV-SPEC;
}

The statements within a watcher block are:

path PATHNAME [recursive [NUMBER]];
Defines a pathname to watch. PATHNAME must be the name of an existing directory in
the file system. The watcher will watch events occurring for all files within that
directory. If the optional recursive clause is specified, this directory will be
watched recursively, i.e. when any subdirectory is created in it, direvent will
set up a watcher for files in this subdirectory. This new watcher will be an exact
copy of the parent watcher, excepting for the pathnames. The optional NUMBER
parameter defines a cut-off nesting level for recursive watching. If supplied, the
recursive behaviour will apply only to the directories that are nested below that
level.

Any number of path statements can appear in a watcher block. At least one path
must be defined.

file STRING-LIST;
Selects which files are eligible for monitoring. The argument is a list of
globbing patterns (in the sense of fnmatch(3)) and/or extended regular expressions
( regex(7)) one of which the file name must match in order for the watcher to act
on it. Regular expressions must be surrounded by a pair of slashes, optionally
followed by the following flags:

b Use basic regular expressions.

i Enable case-insensitive matching.

A pattern or regular expression prefixed with ! matches file names that
don't match the pattern without !.

event STRING-LIST;
Configures the filesystem events to watch for in the directories declared by the
path statements. The argument is a list of event names. Both generic and system-
dependent event namess are allowed. Multiple event statements accumulate. A
missing event statements means watch all events. For example:

event (open,delete);

command STRING;
Defines a command to execute on event. STRING is a command line just as you would
type it in sh(1). It may contain macro variables, which will be expanded prior to
execution. For example:

command "/bin/prog -event $genev_name -file $file";

See the section HANDLER ENVIRONMENT in direvent(8), for a detailed discussion of
how the command is executed.

user STRING;
Run command as this user.

timeout NUMBER;
Terminate the command if it runs longer than NUMBER seconds. The default is 5
seconds.

option STRING-LIST;
A list of additional options. The following options are defined:

wait Wait for the program to terminate before handling next event from
the event queue. Normally the program runs asynchronously.

stdout Capture the standard output of the command and redirect it to the
syslog with the LOG_INFO priority.

stderr Capture the standard error of the command and redirect it to the
syslog with the LOG_ERR priority.

environ ENV-SPEC;
Modify command environment. By default the command inherits the environment of
direvent augmented with the following variables:

DIREVENT_SYSEV_CODE
The system-dependent event code (see the ${sysev_code} variable).

DIREVENT_SYSEV_NAME
The system-dependent event name or names (see the ${sysev_name}
variable).

DIREVENT_GENEV_CODE
The generic event code (see the ${genev_code} variable).

DIREVENT_GENEV_NAME
The generic event name or names (see the ${genev_name} variable).

DIREVENT_FILE
The name of the affected file relative to the current working directory
(see the ${file} variable).

The environ statement allows for trimming the environment. Its argument is a list
of one or more of the folloeing environment modification directives:

- (a single dash)
Clear the inherited environment, but retain the variables added by
direvent. The removed environment variables can be selectively restored
by the directives that follow. This must be the first directive in the
list.

-- (double-dash)
Clear the entire environment, including the variables added by direvent.
This must be the first directive in the list.

-NAME Unset the variable NAME.

-NAME=VAL
Unset the environment variable NAME only if its value is VAL.

NAME Restore the environment variable NAME. This directive is useful after -
or -- to retain some variables from the environment.

NAME=VALUE
Define environment variable NAME to the VALUE. VALUE can contain macro
variables, which will be expanded prior to the assignment.

NAME+=VALUE
Retain the variable NAME and append VALUE to its existing value. If no
such variable is present in the environment, it will be created and
assigned the VALUE. If VALUE begins with a punctuation character, this
character is removed from it before the assignment. This is convenient
for using this construct with environment variables like PATH, e.g.:

PATH+=:/sbin

In this example, if PATH exists, :/sbin will be appended to it.
Otherwise, it will be created and assigned the value /sbin.

The VALUE can contain macro variables, which will be expanded prior to
the assignment.

NAME=+VALUE
Retain the variable NAME and prepend VALUE to its existing value. If no
such variable is present in the environment, it will be created and
assigned the VALUE. In this case, if VALUE ends with a punctuation
character, this character will be removed from it before the assignment.